Referring to FIG. 1, a typical storage system 10 includes at least one rack 12 of storage devices or enclosures 14, 14′. The storage system 10 can have fewer or more enclosures than those shown (internal or external to the rack 12). In general, the enclosure 14 is a storage device having a plurality of disk modules 18. Examples of storage devices include disk-array enclosures (DAE) and disk-array processor enclosures (DPE). A typical DAE includes a plurality of disk modules (e.g., fifteen), one or two link control cards (LCCs), and one or two power supplies. A typical DPE includes a plurality of disk modules (e.g., fifteen), one or two storage processors, one or two LCCs, and one or two power supplies. Disk modules 18 include a carrier assembly that holds a disk drive and slides into the enclosure 14.
Each enclosure 14, 14′ implements redundancy with an “A” side and a “B” side. In enclosure 14, for example, each side has a link control card (LCC) 22, 22′ and a power supply (not shown). Reference numerals for the B side components are the same as corresponding components on the A side with the addition of a prime (′) designation. Each LCC 22, 22′ includes a primary communications port 26, 26′ and an expansion communications port 30, 30′. The enclosures 14, 14′ are connected to each other by cables 34, 34′ in a loop topology. Communication signals traverse the loop in one direction and pass from enclosure 14 to enclosure 14′, in a daisy-chain fashion, and then return from enclosure 14′ to enclosure 14. An enclosure receiving communication signals targeted for another enclosure forward those signals along the loop.
A common implementation of the loop is a Fibre Channel (FC) arbitrated loop. Fibre Channel is a computer communications protocol for communicating signals at a data rate of up to 2 Gbps. In general, the Fibre Channel protocol provides an interface by which host processors (and servers) communicate with the enclosures 14 and with the disk modules 18 installed within the enclosures 14. Typically, the disk modules 18 have Fibre Channel disk drives.
FIG. 2 shows a typical FC enclosure 14 having an FC disk drive 50, the A-side FC LCC 22 and the B-side FC LCC 22′ of FIG. 1. The FC disk drive 50 has two ports (dual port); that is, communications with the disk drive 50 can occur over either port. The FC disk drive 50 is electrically connected to a midplane 54 by a midplane connector 58. The FC LCCs 22, 22′ are also electrically connected to the midplane 54. One FC LCC 22 is in electrical communication with the disk drive 50 by way of one port, and the other FC LCC 22′ is in electrical communication with the FC disk drive 50 by way of the other port.
Disk drive manufacturers have for many years produced another type of disk drive, called Advanced Technology Attachment (ATA) drives, for the personal computer (PC) industry. To satisfy the high volumes and the small profit margins of personal computers, the disk drive manufacturers have refined their processes so as to improve the reliability and storage capacity of the ATA drives, while driving down their cost. Consequently, ATA disk drives present an attractive alternative to FC disk drives for storage system developers and have found their way into storage systems.
To use ATA disk drives in the type of storage system described above requires some adaptations. For one, ATA disk drives are single ported, and therefore are not a direct substitute for the dual ported FC disk drives. To accommodate single port ATA disk drives, the storage industry devised an interface to provide the dual-port operation. Over time, the interface design and operation change to keep pace with revisions, for example, to the disk drive, improvements to the code running on the interface, and bug fixes. Also, at different times in the life of a storage system, some ATA disk drives can be installed with different versions of the interface, and others ATA disk drives can be replaced due to failure or upgrades.
Consequently, a storage system can have several ATA disk drives performing under the control of different revisions of software. Occasionally, when servicing a storage system for repair or for installing an upgrade, a serviceman desires to know the particular revisions of software running on the interfaces of the many disk drives in the system. Visually inspecting each disk drive interface to read the revision information or redesigning standardized equipment to achieve this purpose is neither practical nor cost effective.